Patent GB-710874-A (GB)
Title: Improvements in an inking mechanism for offset lithographic printing machines
Inventor: BRUNS HERBERT FREDERICK
IPC: B41F31/00
Filed: 1951-04-25
Abstract: 710,874. Inking-mechanism. DITTO, Inc. April 25, 1951, No. 9657/51. Class 100 (2) .Inking mechanism for a rotary offset lithographic printing machine includes a vibrator roll 7 and a forme roll 8, which are self-adjusting to increase the pressure between them proportionally with an increase in ink viscosity; the two rolls are simultaneously movable toward and away from the plate cylinder 2, and the vibrator roll 7 is supplied from an ink fountain 4a via (1) a positively driven fountain roll 4, (2) a swinging messenger roll 5, and (3) a non- vibrating rider roll 6 resting on the vibrator roll 7. The invention may be applied to a threecylinder (plate, offset, and impression) machine, or as described to a two-cylinder machine having a two-revolution offset cylinder (not shown) contacting the plate cylinder 2 which has a papercarrying segment. The vibrator roll 7 is mounted in brackets 72 suspended from, and is driven through a toothed belt 81 by a shaft 75 rotated anti-clockwise, Fig. 7, so that increased drag due to increased ink viscosity loads the brackets whereby they tend to swing anti-clockwise and thus increase the pressure exerted by the roll 7 on the roll 8. For easy removal the shaft 77, Fig. 13, of the roll 7 has a spring- pressed sleeve 79 on each end, which is anchored by a diametrical pin in the shaft 77 and engages a second diametrical pin in a stub shaft 78 driven by the belt 81 ; the shaft 78 rotates in bearings in the bracket 72 and in an angle member 76 secured thereto, and each bracket 72 is fixed to a sleeve 73 free on, and extending to the centre of, the shaft 75 ; the two sleeves 73 may be clamped together at their abutting ends, or may be unconnected to allow the roll 7 to find its own level relative to the roll 8 ; one bracket 72 has a pin 83 projecting into an arcuate slot 84 in the machine side frame 13, which is held by a spring-loaded latch 85 when the vibrator roll is swung (clockwise, Fig. 7) into an inoperative position. The shaft 75 is gear and toothed-belt driven from the machine main shaft at such a speed that the vibrator roll 7 and the plate cylinder 2 have the same peripheral speed. It is vibrated by a forked lever 110, Fig. 15, pivoted at 109 and having a spherical roller 112 which follows the groove of a barrel cam 60 gear driven from the fountain roll shaft at such a speed that the vibrator roll 7 is in the mid-portion of its travel when the forme roll 8 is in contact with the printing plate on the cylinder 2. The tubular shaft of the forme roll 8 is mounted by roller &c. bearings on a non- rotary shaft 89, Fig. 7, carried in recesses 92 in hangers 90 pivoted at 91 to the machine side frames and supported by rollers 94 at their lower ends; springs 95 press the roll 8 against the plate cylinder 2 and cams on the latter engage rubber-tyred wheels journalled on the ends of the tubular roll shaft to lift the roll 8 clear of the paper-carrying segment of the cylinder 2; the hangers 90 may be latched back, for removal of the roll 8, by leaf springs 96 engaging pins on the side frames ; the ends of the shafts 89 extend through slots in the side frames into contact with pivoted levers backed by eccentric stops adjustable to set the effective pressure of the roll 8 against the printing plate ; the pivoted levers are also associated with electromagnetically retracted latches which prevent contact of the roll 8 with the printing plate except when a sheet is fed. The end plates 16 of the ink fountain 4a, which are supported by recesses 17 engaging the fountain roll shaft 10 and socketed plates 18 resting on posts 20 projecting from the machine side frames, are joined by an angle frame 21, Fig. 24, and have pins 24 on which is pivoted a bracket 25 carrying the blade 28 ; an adjusting screw (not shown) threaded into the frame 21 moves the bracket 25 about its pivots to vary the overall blade pressure, and individual adjusting screws 31 threaded at intervals into the bracket 25 engage the ends of short bridging rollers 27 to vary the local blade pressure. 'A vertically adjustable duct 146 may be provided at each end of the fountain to draw off moisture globules 163 ; each duct may be connected by flexible conduit to a separate moisture trap, the two traps being connected to a venturi supplied with compressed air, or the ducts may be connected direct to the venturi which is arranged to lead into a single moisture trap open to atmosphere. (1) The shaft 10 of the fountain roll 4 is journalled in bushings in the machine side frames, the side frame openings being large enough to allow the roll 4 to be withdrawn through them; it is driven by a toothed belt from the shaft of the plate cylinder 2, the pulley on the latter having, e.g. 16 grooves while the pulley 131, Fig. 20, on the shaft 10 has one more than 16 or a multiple thereof, e.g. 33, grooves; on the other end of the shaft 10 a gear having, e.g. 33 teeth meshes with a gear 58, Fig. 15, having, e.g. 32 teeth, whereby the pair of cams 59, 60 (see (2) below and the last part of the second paragraph above) are rotated at exactly half the speed of the cylinder 2, while the roll 4 is rotated out-of-phase therewith. The pulley 131, Fig. 20, drives a plate 133 through a shock-absorbing spring, the plate being connected to the shaft 10 through pawl-and-ratchet gear whereby the machine as a whole, but not the fountain roll 4, may be rotated in reverse; in order to retain the cams 59, 60 in phase with the cylinder 2, however, this pawl-and-ratchet gear is indirect ; a spring-loaded pawl 139 engages an abutment 138 on the hub of a 32- tooth planetary gear 137 meshing with a 33- tooth sun gear 142 fixed to the shaft 10. (2) The reduced ends of the shaft 37 of the messenger roll 5 are supported in legs 38 of a U- shaped bracket (one leg 38 having a slot and spring hook to allow the shaft to be removed) ; at the centre of its long base the U-shaped bracket is pivoted by a clip 40 to a screw 42 in a shaft 41 which passes through wide openings 45 in the legs 38, the roll 5 thus being free to adjust itself to the rolls 4 and 6 ; the shaft 41 is carried in bushings in the machine side frames, and at one end, Fig. 15, carries an arm 49 provided with a follower roller 51 held by a spring 54 against a cam 59 integral with the barrel cam 60; a spring-loaded lost-motion device between the arm 49 and shaft 41 gives a resilient pressure of the roll 5 against the roll 6, or the latter may be made capable of slight movement to the right, Fig. 7, for the same purpose ; a latch engages a finger on the arm 49 to keep the roll 5 out of contact with the fountain roll 4 except when the latch is electromagnetically withdrawn in the normal operation of the machine. (3) The shaft '67 of the rider roll 6 runs in slotted arms 71 projecting from the brackets 72; steel balls 68, Fig. 15, at its ends work against steel discs 69 on the side frames to prevent it from vibrating with the roll 7. All the rollers 4-8 are of rubber vulcanized upon their respective shafts, the roller 4 being relatively hard.